FNDC5 and osteoporosis: Although different types of exercise training have conflicting results on irisin, most studies suggest that high-moderate intensity (Tsuchiya et al., 2014; Rashti et al., 2019; Torre-Saldana et al., 2019) and resistance exercises (Nygaard et al., 2015; Tsuchiya et al., 2015; Kim et al., 2016) lead to more significantly enhanced in irisin level, and improve bone loss in patients with osteoporosis (Watson et al., 2019).